private static int firstChoice(Choice ch)
{
if (Options.getForceLaCheck()) {
return 0;
}
for (int i = 0; i < ch.Choices.Count; i++) {
if (!explicitLA((Expansion) ch.Choices[i])) {
return i;
}
}
return ch.Choices.Count;
}
public static IList <MatchInfo> genFirstSet(IList <MatchInfo> partialMatches, Expansion exp)
{
if (exp is RegularExpression)
{
IList <MatchInfo> retval = new List <MatchInfo>();
for (int i = 0; i < partialMatches.Count; i++)
{
MatchInfo m = (MatchInfo)partialMatches[i];
MatchInfo mnew = new MatchInfo();
for (int j = 0; j < m.firstFreeLoc; j++)
{
mnew.match[j] = m.match[j];
}
mnew.firstFreeLoc = m.firstFreeLoc;
mnew.match[mnew.firstFreeLoc++] = ((RegularExpression)exp).Ordinal;
if (mnew.firstFreeLoc == MatchInfo.laLimit)
{
sizeLimitedMatches.Add(mnew);
}
else
{
retval.Add(mnew);
}
}
return(retval);
}
else if (exp is NonTerminal)
{
NormalProduction prod = ((NonTerminal)exp).Production;
if (prod is CodeProduction)
{
return(new List <MatchInfo>());
}
else
{
return(genFirstSet(partialMatches, prod.Expansion));
}
}
else if (exp is Choice)
{
IList <MatchInfo> retval = new List <MatchInfo>();
Choice ch = (Choice)exp;
foreach (Expansion e in ch.Choices)
{
IList <MatchInfo> v = genFirstSet(partialMatches, e);
listAppend(retval, v);
}
return(retval);
}
else if (exp is Sequence)
{
IList <MatchInfo> v = partialMatches;
Sequence seq = (Sequence)exp;
foreach (Expansion unit in seq.Units)
{
v = genFirstSet(v, unit);
if (v.Count == 0)
{
break;
}
}
return(v);
}
else if (exp is OneOrMore)
{
IList <MatchInfo> retval = new List <MatchInfo>();
IList <MatchInfo> v = partialMatches;
OneOrMore om = (OneOrMore)exp;
while (true)
{
v = genFirstSet(v, om.Expansion);
if (v.Count == 0)
{
break;
}
listAppend(retval, v);
}
return(retval);
}
else if (exp is ZeroOrMore)
{
IList <MatchInfo> retval = new List <MatchInfo>();
listAppend(retval, partialMatches);
IList <MatchInfo> v = partialMatches;
ZeroOrMore zm = (ZeroOrMore)exp;
while (true)
{
v = genFirstSet(v, zm.Expansion);
if (v.Count == 0)
{
break;
}
listAppend(retval, v);
}
return(retval);
}
else if (exp is ZeroOrOne)
{
IList <MatchInfo> retval = new List <MatchInfo>();
listAppend(retval, partialMatches);
listAppend(retval, genFirstSet(partialMatches, ((ZeroOrOne)exp).Expansion));
return(retval);
}
else if (exp is TryBlock)
{
return(genFirstSet(partialMatches, ((TryBlock)exp).Expansion));
}
else if (considerSemanticLA &&
exp is Lookahead &&
((Lookahead)exp).ActionTokens.Count != 0
)
{
return(new List <MatchInfo>());
}
else
{
IList <MatchInfo> retval = new List <MatchInfo>();
listAppend(retval, partialMatches);
return(retval);
}
}
public static void choiceCalc(Choice choice)
{
int first = firstChoice(choice);
// dbl[i] and dbr[i] are lists of size limited matches for choice i
// of choice. dbl ignores matches with semantic lookaheads (when force_la_check
// is false), while dbr ignores semantic lookahead.
IList<MatchInfo>[] dbl = new IList<MatchInfo>[choice.Choices.Count];
IList<MatchInfo>[] dbr = new IList<MatchInfo>[choice.Choices.Count];
int[] minLA = new int[choice.Choices.Count - 1];
MatchInfo[] overlapInfo = new MatchInfo[choice.Choices.Count - 1];
int[] other = new int[choice.Choices.Count - 1];
MatchInfo m;
IList<MatchInfo> v;
bool overlapDetected;
for (int la = 1; la <= Options.getChoiceAmbiguityCheck(); la++) {
MatchInfo.laLimit = la;
LookaheadWalk.considerSemanticLA = !Options.getForceLaCheck();
for (int i = first; i < choice.Choices.Count - 1; i++) {
LookaheadWalk.sizeLimitedMatches = new List<MatchInfo>();
m = new MatchInfo();
m.firstFreeLoc = 0;
v = new List<MatchInfo>();
v.Add(m);
LookaheadWalk.genFirstSet(v, (Expansion) choice.Choices[i]);
dbl[i] = LookaheadWalk.sizeLimitedMatches;
}
LookaheadWalk.considerSemanticLA = false;
for (int i = first + 1; i < choice.Choices.Count; i++) {
LookaheadWalk.sizeLimitedMatches = new List<MatchInfo>();
m = new MatchInfo();
m.firstFreeLoc = 0;
v = new List<MatchInfo>();
v.Add(m);
LookaheadWalk.genFirstSet(v, (Expansion) choice.Choices[i]);
dbr[i] = LookaheadWalk.sizeLimitedMatches;
}
if (la == 1) {
for (int i = first; i < choice.Choices.Count - 1; i++) {
Expansion exp = (Expansion) choice.Choices[i];
if (Semanticize.EmptyExpansionExists(exp)) {
CSharpCCErrors.Warning(exp,
"This choice can expand to the empty token sequence " +
"and will therefore always be taken in favor of the choices appearing later.");
break;
} else if (CodeCheck(dbl[i])) {
CSharpCCErrors.Warning(exp,
"CSHARPCODE non-terminal will force this choice to be taken " +
"in favor of the choices appearing later.");
break;
}
}
}
overlapDetected = false;
for (int i = first; i < choice.Choices.Count - 1; i++) {
for (int j = i + 1; j < choice.Choices.Count; j++) {
if ((m = overlap(dbl[i], dbr[j])) != null) {
minLA[i] = la + 1;
overlapInfo[i] = m;
other[i] = j;
overlapDetected = true;
break;
}
}
}
if (!overlapDetected) {
break;
}
}
for (int i = first; i < choice.Choices.Count - 1; i++) {
if (explicitLA((Expansion) choice.Choices[i]) && !Options.getForceLaCheck()) {
continue;
}
if (minLA[i] > Options.getChoiceAmbiguityCheck()) {
CSharpCCErrors.Warning("Choice conflict involving two expansions at");
Console.Error.Write(" line " + ((Expansion) choice.Choices[i]).Line);
Console.Error.Write(", column " + ((Expansion) choice.Choices[i]).Column);
Console.Error.Write(" and line " + ((Expansion) choice.Choices[other[i]]).Line);
Console.Error.Write(", column " + ((Expansion) choice.Choices[other[i]]).Column);
Console.Error.WriteLine(" respectively.");
Console.Error.WriteLine(" A common prefix is: " + image(overlapInfo[i]));
Console.Error.WriteLine(" Consider using a lookahead of " + minLA[i] + " or more for earlier expansion.");
} else if (minLA[i] > 1) {
CSharpCCErrors.Warning("Choice conflict involving two expansions at");
Console.Error.Write(" line " + ((Expansion) choice.Choices[i]).Line);
Console.Error.Write(", column " + ((Expansion) choice.Choices[i]).Column);
Console.Error.Write(" and line " + ((Expansion) choice.Choices[other[i]]).Line);
Console.Error.Write(", column " + ((Expansion) choice.Choices[other[i]]).Column);
Console.Error.WriteLine(" respectively.");
Console.Error.WriteLine(" A common prefix is: " + image(overlapInfo[i]));
Console.Error.WriteLine(" Consider using a lookahead of " + minLA[i] + " for earlier expansion.");
}
}
}
public void Action(Expansion e)
{
if (e is Sequence) {
if (e.Parent is Choice || e.Parent is ZeroOrMore ||
e.Parent is OneOrMore || e.Parent is ZeroOrOne)
return;
Sequence seq = (Sequence) e;
Lookahead la = (Lookahead) (seq.Units[0]);
if (!la.IsExplicit)
return;
// Create a singleton choice with an empty action.
Choice ch = new Choice();
ch.Line = la.Line;
ch.Column = la.Column;
ch.Parent = seq;
Sequence seq1 = new Sequence();
seq1.Line = la.Line;
seq1.Column = la.Column;
seq1.Parent = ch;
seq1.Units.Add(la);
la.Parent = seq1;
Action act = new Action();
act.Line = la.Line;
act.Column = la.Column;
act.Parent = seq1;
seq1.Units.Add(act);
ch.Choices.Add(seq1);
if (la.Amount != 0) {
if (la.ActionTokens.Count != 0) {
CSharpCCErrors.Warning(la,
"Encountered LOOKAHEAD(...) at a non-choice location. " +
"Only semantic lookahead will be considered here.");
} else
CSharpCCErrors.Warning(la, "Encountered LOOKAHEAD(...) at a non-choice location. This will be ignored.");
}
// Now we have moved the lookahead into the singleton choice. Now create
// a new dummy lookahead node to replace this one at its original location.
Lookahead la1 = new Lookahead();
la1.IsExplicit = false;
la1.Line = la.Line;
la1.Column = la.Column;
la1.Parent = seq;
// Now set the la_expansion field of la and la1 with a dummy expansion (we use EOF).
la.Expansion = new REndOfFile();
la1.Expansion = new REndOfFile();
seq.Units[0] = la1;
seq.Units[1] = ch;
}
}